Various and sundry forms of pumps have been taught for producing fluids, in particular oil bearing materials, from well formations. Such pumps as rotary or screw pumps of the type which include a stator affixed to an outer tubing together with a rotor which is driven by a shaft leading from suitable drive mechanism at the surface. The rotor and stator are cooperatively shaped to provide a sufficient pumping pressure to transmit the fluids from the pump through the tubing to the surface where they are further processed.
Examples of pumps of this type are commonly known as Moineau pumps or progressive cavity pumps and will be found in patents such as U.S. Pat. No. 2,085,115; 4,797,075; 4,718,824; and 3,753,628 and many more.
Pumps of this type have been particularly developed for pumping fluids containing particles, i.e. crude oil ladened with sand, which would otherwise easily damage more common type of reciprocating oil well pumping systems. In all instances of the aforesaid pumps of the type described above, these include a rotating drive string (such as a rod string or a tubular string) which is suspended within a stationary tubular production string and rotated such as shown in U.S. Pat. No. 4,372,379.
A Moineau pump with a rotating outer member is found in U.S. Pat. No. 3,932,072 of Clark which teaches the concept of a Moineau pump, not for oil well pumping purposes, in which the outer tubing and normally stator portion of the pump is rotated relative to a fixed rotor. Such a pump system, however, teaches a mechanical means for rotating the normally stator portion.
U.S. Pat. No. 4,614,232 of Jurgens et al. teaches a downhole pump means in which power fluid is used to rotate a rotor within a stator as a part of the drive means which rotor includes a second portion rotor and stator of a pump means wherein the rotor is rigidly a one piece connection.